© 2019 JETIR May 2019, Volume 6, Issue 5 ... · Reinforcement detailing was done as per IS456:2000...

© 2019 JETIR May 2019, Volume 6, Issue 5 www.jetir.org (ISSN-2349-5162)

JETIRCV06079 Journal of Emerging Technologies and Innovative Research (JETIR) www.jetir.org 372

Experimental Study on The Behavior of RC

Corbels Reinforced with GFRP Bars

Ashvin Jacob Varghese Dept. of Civil Engineering

Saintgits College of Engineering Kottayam, Kerala, India

Alice Johny

Dept. of Civil Engineering Saintgits College of Engineering

Kottayam, Kerala, India

Abstract— FRP bars have been adopted as internal

reinforcement of concrete slabs, beams and columns increasing

their service life in unfavourable conditions. FRP bars are more

corrosion resistant than steel bars and shows good resistance to

fatigue loads. The corbel is generally built monolithically with the

column or wall. Here GFRP bars are used as the reinforcement in

the corbel. The preliminary test of cement and aggregates were

done. Compressive strength of concrete cube specimens was

measured. Corbels projecting from the faces of reinforced

concrete columns are extensively used in precast concrete

construction to support the primary beam and girders. Recently,

high strength concrete has been increasing used in practice.

However high strength concrete is considered to be a relatively

brittle material and has low ductility. The tensile strength of

GFRP bar is determined. In this project the study of the behaviour

of RC corbels reinforced with GFRP bars are to be done and

compare it with the control specimen.

Keywords— Corbel, GFRP bars, Reinforcement.

I. INTRODUCTION

The corbel is generally built monolithically with the column or wall. The shear span-to-depth is often less than unity.

Corbels projecting from the faces of reinforced concrete

columns are extensively used in precast concrete construction to

support the primary beam and girders. Corbels are structural

members characterized by a shear span-to-depth ratio (a/d),

generally lower than unity. Recently, high strength concrete has

been increasing used in practice. However high strength

concrete is considered to be a relatively brittle material and has

low ductility.

The fibre-reinforced polymer (FRP) reinforcement is

currently being used as a viable alternative to steel in new concrete structures especially those in harsh environments. The

main driving force behind this effort is the superior performance

of FRP in corrosive environments attributable to its

noncorrodible nature. However, the FRP materials exhibit

linear-elastic stress-strain characteristics up to failure with

relatively low modulus of elasticity [40–60 GPa for glass (G)

FRP compared to 200 GPa for steel]. Moreover, they have

different bond characteristics and relatively low strength under

compressive and shear stresses.

There is large horizontal force transmitted from the

supported beam result from long-term shrinkage and creep

deformation. Bearing failure due to large concentrated load. The cracks are usually vertical or inclined pure shear cracks mode of.

Failure of corbel are: yielding of the tension tie, failure of the end anchorage of the tension tie, failure of concrete by

compression or shearing and bearing failure. Here the reinforcement of corbel is replaced with the GFRP bars. The objective of the study is to understand the behaviour of RC corbels reinforced with GFRP bars and to find out the parameters like shear strength, strain, displacement. GFRP bars are good corrosion resistant when compared to steel bars. It will increase the durability of the structure. By increasing the use of corbels we can reduce the size of the columns.

II. MATERIALS USED

A. Cement

The cement used for the work is Portland Pozzolana Cement

(PPC) – 53 Grade. The details are tabulated in Table 1 below.

Table 1: Properties of Cement

Properties Results

Type of cement PPC 53 grade

Standard Consistency (%) 29

Specific gravity 2.83

B. Fine Aggregate

Manufactured Sand (M-Sand) is used for the work which is conforming to the requirements of IS 383. It is

having aggregate size ranging from 4.75mm to 150microns.

The details are tabulated in Table 2 below. Particle size

distribution of fine aggregate is shown in Fig.1.

Table 2: Properties of Fine Aggregate

Properties Results

Type of fine aggregate M Sand


Zone II

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Fig. 1: Particle Size Distribution of Fine Aggregates

C. Coarse Aggregate

Coarse aggregate used for the work is conforming to the requirements of IS 383 and is having aggregate size

ranging from 20 mm to 4.75 mm. The details are tabulated

in Table 3 below. Particle size distribution of coarse

aggregate is shown in Figure 2.

Table 3: Properties of Coarse Aggregate

Properties Results

Water Absorption 0.5%


Fig. 2: Particle size distribution of coarse aggregate

D. Water

Water used for mixing and curing shall be clean and

free from injurious amounts of oils, acids, alkalies, salts,

sugar, organic materials or other substances that may be

deleterious to concrete or steel. It is an important ingredient

of concrete as it actually participates in the chemical

reaction with cement termed as hydration of cement. Since

it helps to form the strength giving cement gel, the quantity and quality of water are required to be looked into very

carefully. Potable water is generally considered satisfactory

for mixing concrete.

III. MIX DESIGN

The selection of mix proportion is a process of

choosing suitable ingredients of concrete and determining

their relative quantities with the object of producing as

economically as possible, the concrete of certain minimum

properties, notably strength, durability and a required

consistency. The key to achieving strong, durable concrete

rests in the careful proportioning and mixing of the

ingredients. A concrete mixture that has no enough paste to fill all the voids between the aggregates will be difficult to

place and will produce rough, honeycombed surfaces and

porous concrete. A mixture with an excess of cement paste

will be easy to place and will produce a smooth surface,

however the resulting concrete is likely to shrink more and

be uneconomical. A properly designed concrete mix will

possess the desired workability for the fresh concrete and the

durability and strength for the hardened concrete. The mix

design is shown in the table 4.

Table 4: Mix Design

Description Results

Design Mix 1:1.73:3.43

Water-Cement Ratio .0.49

Cement (kg/m 3) 359.73

Fine Aggregate (kg/m 3) 650.7

Coarse Aggregate (kg/m 3) 1286.36

Water(l/m 3) 144

IV. EXPERIMENTAL INVESTIGATIONS

A) Specimen details

Columns of size 0.3 x 0.3 x 1.4 and corbels of size 0.3

x 0.3 x 0.15 were casted monolithically. Corbels with and

without GFRP bars were casted and tested. Table 5 shows the specimen details.

Table 5: Mix Design

Specimen Details Dimensions

i. RCC column ii. 0.3m x 0.3 x 1.4m

iii. RCC corbel iv. 0.3m x 0.3 x 0.15m

B) Reinforcement details

The beam was designed as singly reinforced beam.

The support conditions were simply supported at both

ends. The reinforcement details are given in the figure 3.

Reinforcement detailing was done as per IS456:2000

specification are given in below brief

Ast : 4 no.s of 12mm Ø in column and 6 no.s of 12mm Ø in corbel

5 no.s of 8mm Ø stirrups in both column and

corbel

25mm cover

-20

0

20

40

60

80

100

120

0.01 0.1 1 10

Graph

Obtained

lower limit

Upper limit

0

10

20

30

40

50

60

70

1 10 100

% F

iner

Sieve Size




Fig .3: Reinforcement detail

C) Testing of Specimens

Two ends were fixed. Dial gauges with 10mm capacity

is used. Strain measuring buds were fitted to measure the

strain. For every 2T the deflection and strain are noted

down. The specimens were loaded till failure. The

development of initial crack and propagation of cracks

are observed.

Fig .4: Test Setup

V. RESULTS AND DISCUSSION

The specimen was tested on loading frame, load vs displacement and load vs strain graphs has obtained for

various loads of the control specimen

A. Load vs Deflection Characteristics

The load versus displacement curve was plotted

taking the displacement along the X axis and the load

along Y axis. The graphs were compared with different

specimens as deflection near support and deflection at

centre. It was observed that the displacement increases as

the load increased that is the load and deflection were

directly proportional. In the comparison it shows that the

deflections is proportional to load applied during the initial loading stage and after which there is a sudden increase in

deflection. This shows the deflection increases after the

forming of crack. The load versus displacement of the

control specimen without GFRP bars and specimen with

GFRP bars are shown in figure 5 and 6 respectively.

Fig 5: Load vs Displacement graph of control specimen




Fig 6: Load vs Displacement graph of specimen with GFRP bars

B. Cracks

Crack formation on control specimen is shown in figure 7 and crack formation on specimen with GFRP bars is shown in figure 8.

Fig .7: Crack on Control Specimen

Fig .8: Crack on Specimen with GFRP Bars

VI. CONCLUSION

The control specimen and specimen eth GFRP bars were tested. Based on the investigation the following conclusions were made,

• Load carrying capacity of specimen with GFRP bars are more than control specimen

• Control specimen have more crack than specimen with GFRP bars

• Bending of GFRP bars are difficult.

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[8] Alan H. Mattock,Rafael Alves,(1976) “Design proposals for reinforced concrete corbels”, PCI journal

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[12] V. Carvelli, M. Pisani,(2010), "Fatigue behaviour of concrete

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© 2019 JETIR May 2019, Volume 6, Issue 5 ... · Reinforcement detailing was done as per IS456:2000...

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Transcript of © 2019 JETIR May 2019, Volume 6, Issue 5 ... · Reinforcement detailing was done as per IS456:2000...